Yaddle herself was 477 years old during the events of the Invasion of Naboo, young compared to Yoda's approximately 864 years. She was known for her compassion and patience, as well as her mastery of the ancient and forbidden Jedi art of Morichro, a method for slowing the biological functions of a living being to almost a standstill, but could be dangerously close to the dark side of the Force if used to kill—a skill she taught to very few of her Padawans, due to its obvious capability for being misused. Yaddle also harnessed the power of Force Light. She came across such obscure knowledge through Jedi holocrons while serving as head of the Library Assembly.

Yaddle on Koba, in her younger years.

About 300 BBY, Yaddle was a Padawan of the Jedi Master Polvin Kut, when the two of them traveled to the Koba system to deal with the threat of a local warlord named Tulak. The two Jedi, however, were betrayed by spies and ambushed by the forces of the warlord; Kut was killed and Yaddle was captured. Tulak then imprisoned the diminutive apprentice in a dungeon, far below the surface of the planet Koba. There Yaddle would stay for more than a century, honing her mastery of the Force, ready for her eventual chance to escape—which came when a massive groundquake struck, allowing her to forge to the surface. Instead of immediately returning to Coruscant, however, she remained on the planet and helped the Kodans rebuild their decimated society. These efforts attracted the attention of Tulak's heir, Kalut, who fought with Yaddle. Yaddle defeated the tyrant and in the process liberated the people of Koda once and for all.

When Yaddle eventually returned to Coruscant, the Jedi Council determined her survival of a century of imprisonment and subsequent liberation of Koda were sufficient grounds not only to promote her instantly to the rank of full Jedi Master, but also to offer her a temporary seat on the Jedi Council. During this time, Yaddle trained dozens of Padawans, including Oppo Rancisis, a Thisspiasian who later also went on to serve on the Council, and Empatojayos Brand, who survived the Great Jedi Purge. She was also a proficient healer and diplomat and went on many missions to mediate disputes. Yaddle spent some of her time on Coruscant, but also instructed at an auxiliary Jedi training center on Kamparas for Jedi Knights that did not live on Coruscant full time.

Yaddle, who was 484 at the time of her death, was killed shortly before the Clone Wars, when she used the Force to absorb a deadly chemical weapon, in the process saving the city of Naatan (in which Jedi Knight Obi-Wan Kenobi and his apprentice Anakin Skywalker were staying), but also dying instantly. The chemical weapon was released by Granta Omega.